1. Field of the Invention
The present invention relates to an organic luminescence device having at least an organic compound layer between an anode and a cathode, and an organic luminescence device array and an organic luminescence device package.
2. Related Background Art
An organic luminescence device means a so-called organic electroluminescence device in which a current flowing between a cathode and an anode causes light emission of an organic compound present between the electrodes.
(First Background Art)
FIG. 1 shows a general cross-sectional structure of an organic luminescence device, in which shown are a substrate 1, an electrode 2, a hole transporting layer 3, a light emitting layer 4, an electron injecting layer 5, and a transparent electrode 6.
In such organic luminescence device, electrons injected from the transparent electrode 6 through the electron injecting layer 5 into the light emitting layer 4 combine with positive holes injected from the electrode 2 through the hole transporting layer 3 into the light emitting layer 4 to form excitons, and the device utilizes light emitted when the excitons return to a ground state. The light is emitted to the exterior through the transparent electrode 6.
(Second Background Art)
FIG. 2 shows a general cross-sectional structure of an organic luminescence device array having a plurality of such organic luminescence devices, in which shown are a substrate 1, an electrode 2, a hole transporting layer 3, a light emitting layer 4, an electron injecting layer 5, and a transparent electrode 6, an insulating member 7 provided in an isolating area present between the respective organic luminescence devices, a wiring 8 connected to the electrode 2 of each organic luminescence device, and a resinous member 9. FIG. 2 shows a device having five organic luminescence devices as an example, but the number of the organic luminescence devices provided in an array device can be arbitrarily selected.
(Third Background Art)
FIG. 3 shows a general cross-sectional structure of an organic luminescence device and a package therefor, in which shown are a substrate 1, an electrode 2, a hole transporting layer 3, a light emitting layer 4, an electron injecting layer 5, and a transparent electrode 6 and a case 14 for accommodating the organic luminescence device.
In such organic luminescence device, electrons injected from the transparent electrode 6 through the electron injecting layer 5 into the light emitting layer 4 combine with positive holes injected from the electrode 2 through the hole transporting layer 3 into the light emitting layer 4 to form excitons, and the device utilizes light emitted when the excitons return to a ground state.
(Drawbacks Associated with the First Background Art)
In such organic luminescence device, the transparent electrode 6 is formed by a material of a refractive index higher than that of air or nitrogen, constituting the external environment of the organic luminescence device. Therefore, the light emitted from the light emitting layer 4 is reflected at a light emitting surface of the transparent electrode 6, namely at the interface between the transparent electrode and the air constituting the externals environment in FIG. 1. For this reason, such organic luminescence device has been associated with a low efficiency of light emission to the exterior, and, in case of employing a transparent electrode 6 formed by a material of such high refractive index, an external light falling on the organic luminescence device from the external environment is reflected at the interface of the transparent electrode 6 and the external environment, whereby, even if the other electrode 2 formed at the substrate side is provided with means for preventing reflection of the external light, the external light is reflected on the surface of the transparent electrode 6 to cause a mixing of the light emitted by the device and the reflected light of the external light thereby lowering the contrast of the organic luminescence device. Also in case a passivation film such as a SiN film for moisture prevention is formed on the transparent electrode 6, a similar drawback is encountered because of a large difference in the refractive index between the SiN film and the air.
(Drawback Associated with the Second Background Art)
In an organic luminescence device array having a plurality of such organic luminescence devices, there is formed a wiring connected to the electrode of each organic luminescence device, in an isolation area of the organic luminescence devices and under the organic luminescence devices. In case an insulating member 7 provided in such isolation area and a resinous member 9 on the substrate 1 are light transmissible, the external light entering the organic luminescence device array from the external environment is transmitted by the insulating member 7 in the isolation area and the resinous member 9 and is reflected by the wiring 8. Also the external light may be reflected by such-insulating member 7 or resinous member 9. The light reflected in these portions is mixed with the light emitted from the organic luminescence device to lower the contrast thereof, whereby an image displayed by the device is deficient in visibility.
Also in a package accommodating the aforementioned organic luminescence device array in a case, in order to avoid the aforementioned drawback of the contrast loss by the reflection of the external light, it is necessary to form a polarizing layer on a light emitting face of the case. For this reason, the package of such organic luminescence device array is also associated with a drawback that the manufacture is complex and expensive.
(Drawback Associated with the Third Background Art)
In a package of such organic luminescence device, the light emitted from the light emitting layer 4 is transmitted by the transparent electrode 6, and enters the light emitting face of the case 14 through an unrepresented atmospheric gas such as air or nitrogen. The case 14 is generally formed with a material such as glass or resin, of which refractive index is higher than of the atmospheric gas present between the organic luminescence device and the case. Therefore, the light emitted from the light emitting layer 4 is partly reflected at the interface between the atmospheric gas and the light entering face of the case 14. For this reason, such package of the organic luminescence device has been associated with a low efficiency of light emission to the exterior.
Similarly, the transparent electrode 6 has a refractive index higher than that of the unrepresented atmospheric gas. Therefore, the light emitted from the light emitting layer 4 is partly reflected at the interface between the transparent electrode 6 and the atmospheric gas, and such package of the organic luminescence device has been associated with a low efficiency of light emission to the exterior.
Furthermore, for the case 14, the material constituting the case 14 has a refractive index higher than that of the air constituting the external environment of the package, whereby the light from the external environment (external light) is reflected on the face of the case 14, emitting the light. For this reason, the light emitted from the device is mixed with the external light at the interface between the external environment and the case 14, whereby the organic luminescence package itself has a low contrast.